createrelease: use -j12 to build faster, build with -O2

[danmar]

No description provided.

[firewave]

That should use $(nproc) so it will use the actual available cores.

[danmar]

That should use $(nproc) so it will use the actual available cores.

however I don't want to use all cores. that can affect my user experience negatively when I do something with the computer meanwhile..

[firewave]

You can use something like this to just use 80% of the cores:

np=$(nproc)
np=$((np * 8))
np=$((np / 10))